Hypertension is a major health risk associated with obesity. Weight loss therapy, combined with exercise and behavior modification, may be a practical alternative to pharmacologic therapy for certain categories of obese, hypertensive patients. The study proposed will determine the effects on blood pressure in 300 obese, hypertensive men and women of two different outpatient dietary interventions that restrict calories (two 600 calorie diets with and without carbohydrate) compared to a control diet of moderate restriction (1500 calories). Sodium, potassium, and calcium excretion will be measured allowing investigation of the possible impact of salt beyond that of weight reduction alone. The association between the dietary interventions and blood pressure due to weight loss will be quantified both during active treatment and for 2 years of follow-up. An inpatient study of 42 subjects will also be conducted to investigate hypotheses relating to metabolic differences between the three diets. In addition, psychological correlates of weight loss will be investigated in the outpatient study using standardized tests to measure mood, depression, self-concept, and overall personality traits. The results of this research can be expected to improve the safety and effectiveness of non-pharmacologic treatment of obese hypertensives and to provide data to help identify subgroups amongst the obese population who may be effectively treated with weight reduction programs.